/Engine/Plugins/Animation/MLDeformer/MLDeformerFramework/Source/MLDeformerFrameworkEditor/Public/MLDeformerEditorModel.h
Calculate the normals for each vertex, given the triangle data and positions. It computes this by summing up the face normals for each vertex using that face, and normalizing them at the end.
void CalcMeshNormals ( [TArrayView](API\Runtime\Core\Containers\TArrayView)< const FVector3f > VertexPositions, [TArrayView](API\Runtime\Core\Containers\TArrayView)< const uint32 > IndexArray, [TArrayView](API\Runtime\Core\Containers\TArrayView)< const int32 > VertexMap, [TArray](API\Runtime\Core\Containers\TArray)< FVector3f > & OutNormals ) const